A sulfone is a molecule that has a sulfur atom with bonds to two oxygen atoms. The sulfur has two double bonds to the two oxygens. It has a single bond with the other two groups. They are usually made by oxidising thioethers.
They are used in many important chemical reactions. For example, the Julia olefination uses a sulfone to make an alkene from an aldehyde. They are also sometimes used as solvents.